What is meant by 'search engine spam'?
The same question comes up time and time again - "Is this spam?". What the question really means is, "Is this wrong or unethical?", although sometimes the question may mean, "Is this going to get my site penalized?".
The fact is that none of the so-called spam techniques and methods are in any way wrong or unethical . A technique or method only becomes wrong or unethical when it is used unethically; e.g. a page that appears to be about one thing but which automatically redirects people to something quite different.
An example of a search engine optimization method that some consider to be spam/wrong/unethical is hidden text. The idea behind hidden text is to show some optimized text to the search engines but not to people viewing the page in a browser. It is done because the text wouldn't make much sense to the viewer or it would spoil the design of the page. But there is nothing wrong with this technique. It doesn't attempt to hide anything from the search engines. The fact that they don't want it is irrelevant. The text is in plain sight to them and their programs. If they don't spot it, that's their problem.
What should be realized about all the so-called search engine spam techniques is that they don't hurt anyone. In fact they help everybody. Unless they are used unscrupulously, they help a page to be ranked more highly for its actual topic than it otherwise would. Surfers find the page in the search results and go to the page's site. There they find what they expected to find, having read the page's search engine listing. The surfer is happy, the search engine should be happy because it sent a surfer to a relevant site, and the page owner is happy because s/he has a site visitor.